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  <script>

    /* 形参默认值的正确打开方式 */
    // function fn(a = 10) {
    //   console.log(a * 2)
    // }
    // fn()

    /* 形参默认值的正确打开方式 */
    // let fn = (a=10,b=20)=>console.log(a,b)
    // fn(11)

  </script>
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